If your dates are very consistently formatted like that, then you can probably just create a regex to extract all the parts and reformat it. It's a decent intro regex problem.

If your dates are more complicated (e..g Third tuesday of the month) then Date::Manip is probably a good starting point. Sometimes Date::Manip doesn't have quite what you need a little pre-processing of your target data using a regex before you feed it to Date::Manip. It will probably also handle your dates as formatted, maybe with a little preprocessing.

Thanks for the suggestion. This is the Regex that I've come up with:

if($_=~/Launching the JVM/){
/\-+ [A-Za-z]{3} (.*?) (.*?) (.*?)\:(.*?)\:(.*?) (\d+)::(\d+)::Launchi
+ng the JVM with following options/;

 if ( $1 eq "Jan") { $month= "01";}
 if ( $1 eq "Feb") { $month= "02";}
...
 if ( $1 eq "Dec") { $month= "12";}

 if ( $2 eq " 1") { $start_date= "01";}
 if ( $2 eq " 2") { $start_date= "02";}
...
 if ( $2 eq " 9") { $start_date= "09";}

 if ( $3 eq " 1") { $start_hour= "01";}
 if ( $3 eq " 2") { $start_hour= "02";}
...
 if ( $3 eq " 9") { $start_hour= "09";}

 if ( $4 eq "1") { $start_min= "01";}
 if ( $4 eq "2") { $start_min= "02";}
...
 if ( $4 eq "9") { $start_min= "09";}

 if ( $5 eq "1") { $start_sec= "01";}
 if ( $5 eq "2") { $start_sec= "02";}
...
 if ( $5 eq "9") { $start_sec= "09";}

print "App Start time is: $6-$month-$start_date $start_hour:$start_min
+:$start_sec\n";
[download]

However, it is failing to convert if the date / hour / min / sec is a single digit / character 0-9 and prints it something like:

$perl get_ts.pl

--------------------------------------

App Start time is: 2015-04- 8 1:51:20

--------------------------------------

Not sure what I am doing wrong. I tried replacing .*? to \d+ but still not getting the desired results.

Can you please suggest?

You should check whether the match succeeds at all.

if (/\-+ [A-Za-z]{3} (.*?) (.*?) (.*?)\:(.*?)\:(.*?) (\d+)::(\d+)::Lau
+nching the JVM with following options/) {
    ...
[download]

Also, use hashes and sprintf to format the numbers and convert month names:

# Declaration
my $m = 1;
my %MONTH = map { $_ => $m++ } qw( Jan Feb Mar Apr May ... );

# Later in the code:
$month = sprintf '%02d', $MONTH{$1};
[download]

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

Hello jayu_rao, and welcome to the Monastery!

If your log file is very large, you should consider using the module File::ReadBackwards, which is designed for this kind of task. Here is a code outline (skeleton) to get you started (you need to fill in the parts marked ...):

use strict;
use warnings;
use File::ReadBackwards;

my $log   = ...;
my $fh    = File::ReadBackwards->new($log) or die "Cannot read '$log':
+ $!";
my $found = 0;

while (my $line = $fh->readline)
{
    if ($line =~ /.../)     # Identify a JVM line and capture the time
+stamp
    {
        ...;                # Re-format the timestamp and export it
        $found = 1;
        last;
    }
}

warn "No log entry found\n" unless $found;
[download]

Hope that helps,

Thanks much Athanasius. I had used read backwards :-) and needed assistance in extracting the timestamp. Can you please look at the regex that I have come up with, in my code and suggest what is it that I am doing wrong?

Hello jayu_rao,

When comparing strings using eq, the match has to be exact to succeed. For the data line:

----- Sun Mar 8 10:51:20 2015::4426::Launching the JVM with following 
+options.
[download]

your regex is capturing $2 as "8" (a single character, no initial space). So when you come to compare it:

if ( $2 eq " 8") { $start_date= "08";}
[download]

the match fails. Two useful references:

• Basic debugging checklist
• Unbelievably Obvious Debugging Tip

But please follow choroba’s advice and use a hash lookup instead of a regex for this kind of conversion. Remember the Perl motto: when in doubt, use a hash! :-)

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

#!/usr/bin/env perl
use strict;
use warnings;
use Time::Piece;

my @dates;

while (<DATA>) {
   next unless /Launching the JVM with following options/;
   my ($date, $line) = split /::/,$_,2;
   $date = Time::Piece->strptime($date, "----- %a %b %d %T %Y");
   push @dates, [ $date, $line ];
}

for (@dates) {
   print $_->[0]->strftime("%Y-%m-%d %T") . " $_->[1]";
}


__DATA__
----- Sun Mar 8 10:51:20 2015::4426::Launching the JVM with following 
+options.
# 2015-03-08 10:51:20 4426::Launching the JVM with following options.
[download]

Thanks trippledubs and every one. Time::Piece helped me with this requirement.

Regards,

Jay